Imaging lens

ABSTRACT

An imaging lens which uses a larger number of constituent lenses for higher performance and features a low F-value, low-profile design and a wide field of view. Designed for a solid-state image sensor, the imaging lens includes constituent lenses arranged in order from an object side to an image side: a first positive refractive power lens; a second negative refractive power lens; a third lens; a fourth lens; a fifth lens; a sixth lens having a concave image-side surface near an optical axis; and a seventh negative refractive power lens.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.14/252,828, filed on Apr. 15, 2014, the contents of which areincorporated herein by reference.

The present application is based on and claims priority of Japanesepatent application No. 2013-130416 filed on Jun. 21, 2013, the entirecontents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to imaging lenses which form an image ofan object on a solid-state image sensor such as a CCD sensor or a C-MOSsensor used in a compact image pickup device. More particularly, theinvention relates to imaging lenses which are built in image pickupdevices mounted in highly functional products such as smart TVs and 4KTVs, information terminals such as game consoles and PCs, and mobileterminals such as smart phones, mobile phones and PDAs (Personal DigitalAssistants).

2. Description of the Related Art

In recent years, highly functional products, such as a smart TV as a TVwith a personal computer function and a 4K TV as a TV with four timeshigher resolution than a full high-definition TV, have been attractingattention. In smart TVs, the tendency toward products which are not onlyhighly functional but also multifunctional is growing, so the smart TVmarket is expected to expand in the future. Some smart TVs provide afunction to take video and still images through a built-in image pickupdevice and transmit the images through a communication network. Thisfunction can be used in various application fields: for example, a videophone and a high-precision people meter based on face recognitiontechnology, and other various products such as a security product and apet monitoring product which have a moving object detection function.Also, due to its high resolution, a 4K TV can reproduce an image whichis so realistic as if the object were there. With the spread of smartTVs or similar products, these functions are expected to be more popularthan before. On the other hand, digital photo frames with a camerafunction have been recently introduced into the market. Thus, the marketrelated to cameras is expected to expand.

In communications over a video phone, for example, in a TV conference inwhich several people participate, the facial expression of the speakerand the surrounding scene are important information. In addition, whenface recognition technology is used to recognize the faces of humanbeings or animals, image recognition should be highly accurate. Theimaging lens used in such a high resolution product is required to havea compact lens system which provides high resolution, a wide field ofview and high brightness.

However, in the conventional techniques, it is difficult to meet thisdemand satisfactorily. For example, the image pickup device used in ahighly functional product such as a smart TV is assumed to adopt arelatively large image sensor suitable for high resolution images. If aconventional imaging lens is used in a large image sensor, since itsoptical system should be large, the following problem arises thatvarious aberrations become more serious and it is very difficult toachieve the same level of high optical performance as in a small imagesensor. In addition, when the lens is designed to provide a wide fieldof view, correction of aberrations may be very difficult, particularlyin the peripheral area, regardless of image sensor size and it may beimpossible to deliver satisfactory optical performance.

As an imaging lens built in an apparatus with an image pickup device,the imaging lens described in Patent Document 1 (JP-A-2010-262270) orthe imaging lens described in Patent Document 2 (JP-A-2012-155223) isknown.

Patent Document 1 discloses an imaging lens which includes, in orderfrom an object side, a first lens with positive refractive power havinga convex shape on the object-side surface near an optical axis, a secondlens with negative refractive power, a third lens with positiverefractive power having a concave shape on an image-side surface nearthe optical axis, a fourth lens with positive refractive power having aconvex shape on the image-side surface near the optical axis, and afifth lens with negative refractive power near the optical axis. Theimaging lens described in Patent Document 1 includes five constituentlenses, each of which is optimized to deliver high performance.

Patent Document 2 discloses an imaging lens which includes, in orderfrom an object side, a first lens group with positive refractive power,a second lens group with negative refractive power, a third lens groupwith positive refractive power, a fourth lens group with negativerefractive power, a fifth lens group with positive refractive power, anda sixth lens group with negative refractive power. In the imaging lensdescribed in Patent Document 2, the lens configuration of the opticalsystem is concentric with an aperture stop so as to suppress astigmatismand coma aberrations and provide a wider field of view.

The imaging lens described in Patent Document 1 has a lens system whichprovides high brightness with an F-value of 2.0 and a relatively widefield of view with a half field of view of about 38 degrees. However, itcannot meet the recent demand for a wider field of view. Also, for usein a large image sensor, various aberrations must be further suppressed.However, if an imaging lens uses five constituent lenses, its ability tocorrect aberrations is limited and it is difficult to apply the imaginglens to a higher resolution product as mentioned above.

The imaging lens described in Patent Document 2 provides relatively highbrightness with an F-value of about 2.3 and can correct aberrationsproperly. However, its half field of view is about 33 degrees, whichmeans that it cannot meet the demand for a wide field of viewsatisfactorily. Also, if the lens configuration described in PatentDocument 2 is employed to provide a wide field of view, correction ofaberrations will be difficult, particularly in the peripheral area andhigh optical performance cannot be delivered.

As mentioned above, in the conventional arts, it is difficult to providea sufficiently wide field of view while ensuring compactness, and meetthe demand for high resolution. Also, for use in a large image sensor,it is difficult to deliver the same level of high optical performance asin a conventional small image sensor.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above problem and anobject thereof is to provide a high-brightness compact imaging lenswhich delivers higher optical performance than conventional imaginglenses when it is used not only in a conventional small image sensor butalso in a large image sensor, and provides a wide field of view and cancorrect various aberrations properly.

A “compact” imaging lens here means an imaging lens in which the ratioof total track length TTL to the length (2ih) of the diagonal of theeffective image plane of the image sensor, namely TTL/2ih is 1.0 orless. “Total track length” means the distance from the object-sidesurface of an optical element nearest to an object to the image plane onthe optical axis in an optical system.

According to one aspect of the present invention, there is provided animaging lens in which constituent lenses are arranged in the followingorder from an object side to an image side: a first lens with positiverefractive power, a second lens with negative refractive power, a thirdlens, a fourth lens, a fifth lens, a sixth lens having a concave surfaceon the image side near an optical axis, and a seventh lens with negativerefractive power.

According to another aspect of the present invention, there is providedan imaging lens in which constituent lenses are arranged in thefollowing order from an object side to an image side: a first lens withpositive refractive power having a biconvex shape near an optical axis,a second lens, a third lens, a fourth lens, a fifth lens, a sixth lensas a double-sided aspheric lens having a convex surface on the objectside near the optical axis, and a seventh lens with negative refractivepower as a meniscus double-sided aspheric lens. The imaging lenssatisfies a conditional expression (10) below:

2.0<|f34/f|  (10)

where

-   -   f: focal length of an overall optical system of the imaging        lens, and    -   f34: composite focal length of the third lens and the fourth        lens.

Preferably, in the imaging lens according to the present invention, thefirst lens has a convex surface on the object side near the opticalaxis, and the second lens has a concave surface on the image side nearthe optical axis.

Preferably, in the imaging lens according to the present invention, thethird lens has positive refractive power with a convex surface facingthe image side near the optical axis, and the fourth lens has negativerefractive power with a concave surface facing the image side near theoptical axis.

Preferably, in the imaging lens according to the present invention, thefifth lens is a meniscus lens with positive refractive power having aconvex surface on the image side near the optical axis.

Preferably, in the imaging lens according to the present invention, thesixth lens is a meniscus double-sided aspheric lens, having apole-change point in a position off the optical axis on the object-sidesurface and the image-side surface thereof, and the seventh lens is adouble-sided aspheric lens with a concave surface facing the image sidenear the optical axis, having a pole-change point in a position off theoptical axis on the image-side surface thereof. The above imaging lensincludes a first lens group composed of the first and second lenses, asecond lens group composed of the third and fourth lenses, a third lensgroup composed of a fifth lens, and a fourth lens group composed of thesixth and seventh lenses, which means that it includes four groups withseven constituent lenses in which the lens groups are arranged in orderfrom the object side as follows: positive, positive, positive andnegative lens groups or positive, negative, positive, and negative lensgroups. This refractive power arrangement is effective in shortening thetotal track length. Also, in each of the first and second lens groups,the positive lens is located on the object side and the negative lens islocated on the image side so that chromatic aberrations generated on thepositive lens located on the object side are properly corrected by thenegative lens located on the image side. Also, the fifth lensconstituting the third group has adequate positive refractive power tokeep the total track length short, and the negative sixth and seventhlenses constituting the fourth group have adequate aspheric surfaces tocorrect chromatic aberrations further and properly correct fieldcurvature and distortion and control the angle of a chief ray incidenton the image sensor.

The first lens is a biconvex lens in which the curvature radius of theobject-side surface is smaller than the curvature radius of theimage-side surface and positive refractive power is adequatelydistributed to both the surfaces so as to suppress spherical aberrationsand provide relatively strong refractive power for compactness of theimaging lens. Alternatively the image-side surface of the first lens maybe concave and in that case, it is desirable that the curvature radiusof the image-side surface be larger than the curvature radius of theobject-side surface to the extent that the refractive power is not toolow and spherical aberrations do not increase.

The second lens is a lens with negative refractive power which has aconcave surface on the image side near the optical axis and correctsspherical aberrations and chromatic aberrations properly.

The third lens is a lens with positive refractive power having a convexsurface on the image side near the optical axis, which corrects fieldcurvature and coma aberrations properly.

The fourth lens is a lens with negative refractive power having aconcave surface on the image side near the optical axis, which correctsresidual chromatic aberrations properly.

The fifth lens is a meniscus lens with positive refractive power havinga convex surface on the image side near the optical axis, in which itspositive refractive power is relatively strong among the constituentlenses of the imaging lens. Its refractive power is balanced with thepositive refractive power of the first lens, contributing to thecompactness of the imaging lens.

The sixth lens is a meniscus lens having a concave surface on the imageside near the optical axis, which corrects residual chromaticaberrations properly. The aspheric surfaces on both the sides of thelens contribute to proper correction of coma aberrations andastigmatism.

The seventh lens is a meniscus lens with negative refractive powerhaving a concave surface on the image side near the optical axis, whichensures an adequate back focus easily. Due to the aspheric surfaces onboth the sides of the lens, its negative refractive power graduallydecreases and changes to positive refractive power in the peripheralportion. This is effective mainly in correcting distortion and fieldcurvature and controlling the angle of a chief ray incident on the imagesensor.

Preferably, the imaging lens according to the present inventionsatisfies conditional expressions (1) and (2) below:

50<νd1<70  (1)

20<νd2<30  (2)

where

-   -   νd1: Abbe number of the first lens at d-ray, and    -   νd2: Abbe number of the second lens at d-ray.

The conditional expressions (1) and (2) define adequate ranges for theAbbe numbers of the first and second lenses at d-ray and indicateconditions to correct chromatic aberrations generated on the first lensproperly. If the value is below the lower limit of the conditionalexpression (1) or the value is above the upper limit of the conditionalexpression (2), the difference in dispersion value between the first andsecond lenses would be smaller, making it impossible to correctchromatic aberrations properly. If the value is above the upper limit ofthe conditional expression (1) or the value is below the lower limit ofthe conditional expression (2), the balance between axial chromaticaberration and chromatic aberration of magnification would worsen,making it difficult to deliver the required optical performance in theperipheral portion.

Preferably, the imaging lens according to the present inventionsatisfies conditional expressions (3) and (4) below:

50<νd3<70  (3)

20<νd4<30  (4)

where

-   -   νd3: Abbe number of the third lens at d-ray, and    -   νd4: Abbe number of the fourth lens at d-ray.

The conditional expressions (3) and (4) define adequate ranges for theAbbe numbers of the third and fourth lenses at d-ray and indicateconditions to correct chromatic aberrations generated on the third lensproperly. If the value is below the lower limit of the conditionalexpression (3) or the value is above the upper limit of the conditionalexpression (4), the difference in dispersion value between the third andfourth lenses would be smaller, making it impossible to correctchromatic aberrations properly. If the value is above the upper limit ofthe conditional expression (3) or the value is below the lower limit ofthe conditional expression (4), the balance between axial chromaticaberration and chromatic aberration of magnification would worsen,making it difficult to deliver the required optical performance in theperipheral portion.

Preferably, in the imaging lens according to the present invention, theobject-side surface and image-side surface of the sixth lens areaspheric surfaces having a pole-change point in a position off theoptical axis.

When the object-side surface of the sixth lens is an aspheric surfacehaving a pole-change point and change in the amount of aspheric surfacesag is small, the total track length can be shortened, so the imaginglens can be compact. Also, when the object-side surface and image-sidesurface of the sixth lens are aspheric surfaces having a pole-changepoint in a position off the optical axis, the lens is a meniscus lenshaving a convex surface on the object side near the optical axis inwhich as the distance from the optical axis increases, the shape of theobject-side surface changes from convex to concave and the shape of theimage-side surface changes from concave to convex. An aspheric surfacewhose shape changes in this way can effectively correct aberrations inthe area from the center of the image plane to its maximum image heightpoint. In addition, the sixth lens plays a very important role inreducing the burden on the seventh lens, located nearest to the imageplane, for correction of aberrations and control of the chief ray angle.

Preferably, in the imaging lens according to the present invention, theimage-side surface of the seventh lens is an aspheric surface having apole-change point in a position off the optical axis.

The image-side surface of the seventh lens is an aspheric surface havinga pole-change point in a position off the optical axis and has a concaveshape near the optical axis and its shape changes to convex as thedistance from the optical axis increases. This aspheric shape mainlymakes final correction of distortion and field curvature easy and alsomakes control of the chief ray angle easy, preventing a decline inrelative illumination in the peripheral portion. In the presentinvention, a “pole-change point” means a point on an aspheric surface atwhich a tangential plane intersects the optical axis perpendicularly.

Preferably, the imaging lens according to the present inventionsatisfies a conditional expression (5) below:

0.6<TTL/2ih<1.0  (5)

where

-   -   TTL: distance on the optical axis from an object-side surface of        an optical element located nearest to the object to an image        plane without a filter, etc., and    -   ih: maximum image height.

The conditional expression (5) defines an adequate range for the ratioof total track length to maximum image height of the imaging lens andindicates a condition to achieve compactness and high imagingperformance. If the value is above the upper limit of the conditionalexpression (5), the total track length would be too long, making itdifficult to achieve compactness. On the other hand, if the value isbelow the lower limit of the conditional expression (5), it would beeasier to achieve compactness but the total track length would be tooshort, making it difficult that the constituent lenses of the imaginglens have optimum shapes. As a consequence, it would be difficult tocreate a configuration capable of correcting aberrations properly,leading to deterioration in optical performance.

More preferably, the imaging lens according to the present inventionsatisfies a conditional expression (5a) below:

0.6<TTL/2ih<0.9.  (5a)

Preferably, the imaging lens according to the present inventionsatisfies a conditional expression (6) below:

0.85<Σd/f<1.25  (6)

where

-   -   f: focal length of the overall optical system of the imaging        lens, and    -   Σd: distance on the optical axis from the object-side surface of        the first lens to the image-side surface of the seventh lens.

The conditional expression (6) indicates a condition to shorten thetotal track length and correct aberrations properly. If the value isabove the upper limit of the conditional expression (6), the back focuswould be too short and it would be difficult to provide space for afilter or the like, leading to a longer total track length. On the otherhand, if the value is below the lower limit of the conditionalexpression (6), it would be difficult for each constituent lens of theimaging lens to have the required thickness. In addition, the distancebetween constituent lenses would be smaller, which might restrict thefreedom of aspheric shape design. As a consequence, it would bedifficult to correct aberrations properly, making it difficult todeliver high optical performance. The imaging lens according to thepresent invention includes seven constituent lenses, namely a largernumber of constituent lenses than conventional imaging lenses, and anair gap is provided between constituent lenses. Therefore, generallythis configuration is considered as disadvantageous in achievingcompactness, but when the value falls within the range defined by theconditional expression (6), the imaging lens can be as compact as, ormore compact than, conventional imaging lenses composed of five or sixconstituent lenses.

More preferably, the imaging lens according to the present inventionsatisfies a conditional expression (6a) below:

0.95<Σd/f<1.25.  (6a)

Preferably, the imaging lens according to the present inventionsatisfies a conditional expression (7) below:

0.8<ih/f<1.2  (7)

where

-   -   f: focal length of the overall optical system of the imaging        lens, and    -   ih: maximum image height.

The conditional expression (7) defines an adequate range for the ratioof the focal length of the overall optical system of the imaging lens tomaximum image height and indicates a condition to provide a wide fieldof view and deliver high imaging performance. If the value is above theupper limit of the conditional expression (7), the field of view wouldbe too wide to correct aberrations properly, leading to deterioration inoptical performance. On the other hand, if the value is below the lowerlimit of the conditional expression (7), the focal length of the overalloptical system of the imaging lens would be too long to achievecompactness, offering a disadvantage in providing a wide field of view.

Preferably, the imaging lens according to the present inventionsatisfies conditional expressions (8) and (9) below:

0.7<f1/f<1.5  (8)

−5.0<f2/f<−1.0  (9)

where

-   -   f: focal length of the overall optical system of the imaging        lens,    -   f1: focal length of the first lens, and    -   f2: focal length of the second lens.

The conditional expression (8) defines an adequate range for the ratioof the focal length of the first lens to the focal length of the overalloptical system of the imaging lens and indicates a condition to achievecompactness of the imaging lens and correct spherical aberrations andcoma aberrations properly. If the value is above the upper limit of theconditional expression (8), the positive refractive power of the firstlens would be too weak to achieve compactness of the imaging lens. Onthe other hand, if the value is below the lower limit of the conditionalexpression (8), the positive refractive power of the first lens would betoo strong to correct spherical aberrations and coma aberrationsproperly.

The conditional expression (9) defines an adequate range for the ratioof the focal length of the second lens to the focal length of theoverall optical system of the imaging lens and indicates a condition toachieve compactness of the imaging lens and correct chromaticaberrations properly. If the value is above the upper limit of theconditional expression (9), the negative refractive power of the secondlens would be too strong to achieve compactness of the imaging lens.Also, axial and off-axial chromatic aberrations would be excessivelycorrected, making it difficult to deliver high imaging performance. Onthe other hand, if the value is below the lower limit of the conditionalexpression (9), the negative refractive power of the second lens wouldbe too weak to correct axial and off-axial chromatic aberrationsproperly. In this case as well, it would be difficult to deliver highimaging performance.

Preferably, the imaging lens according to the present inventionsatisfies a conditional expression (10) below:

2.0<|f34/f|  (10)

where

-   -   f: focal length of the overall optical system of the imaging        lens    -   f34: composite focal length of the third lens and the fourth        lens.

The conditional expression (10) defines an adequate range for the ratioof the composite focal length of the third and fourth lenses to thefocal length of the overall optical system of the imaging lens andindicates a condition to correct astigmatism and coma aberrationsproperly. If the value is below the lower limit of the conditionalexpression (10), the composite refractive power of the third and fourthlenses would be too strong to correct astigmatism and coma aberrationsproperly.

Preferably, the imaging lens according to the present inventionsatisfies conditional expressions (11) and (12) below:

0.6<f5/f<1.2  (11)

−1.2<f67/f<−0.6  (12)

where

-   -   f: focal length of the overall optical system of the imaging        lens,    -   f5: focal length of the fifth lens, and    -   f67: composite focal length of the sixth lens and the seventh        lens.

The conditional expression (11) defines an adequate range for the ratioof the focal length of the fifth lens to the focal length of the overalloptical system of the imaging lens and indicates a condition to achievecompactness of the imaging lens and correct coma aberrations and axialchromatic aberrations properly. If the value is above the upper limit ofthe conditional expression (11), the positive refractive power of thefifth lens would be too weak to achieve compactness of the imaging lens.On the other hand, if the value is below the lower limit of theconditional expression (11), the positive refractive power of the fifthlens would be too strong to correct coma aberrations and axial chromaticaberrations properly.

The conditional expression (12) indicates a condition to keep the totaltrack length short, deliver the required performance and ensure anadequate back focus. If the value is above the upper limit of theconditional expression (12), the composite negative refractive power ofthe sixth and seventh lenses would be too weak to ensure an adequateback focus. On the other hand, if the value is below the lower limit ofthe conditional expression (12), the composite negative refractive powerof the sixth and seventh lenses would be too strong to keep the totaltrack length short.

More preferably, the imaging lens according to the present inventionsatisfies conditional expressions (11a) and (12a) below:

0.75<f5/f<1.05  (11a)

−1.1<f67/f<−0.7.  (12a)

Preferably, the imaging lens according to the present inventionsatisfies conditional expressions (13), (14), and (15) below:

50<νd5<70  (13)

20<νd6<30  (14)

50<νd7<70  (15)

where

-   -   νd5: Abbe number of the fifth lens at d-ray,    -   νd6: Abbe number of the sixth lens at d-ray, and    -   νd7: Abbe number of the seventh lens at d-ray.

The conditional expressions (13), (14), and (15) define adequate rangesfor the Abbe numbers of the fifth, sixth, and seventh lenses,respectively and indicate conditions to correct chromatic aberrationsproperly. If these lenses, namely the three lenses nearer to the imageplane among the seven constituent lenses, satisfy the respectiveconditional expressions, it means that the lenses made of low-dispersionmaterial and high-dispersion material are arranged alternately andconsequently axial chromatic aberrations and chromatic aberrations ofmagnification occurred on the image plane side in the lens system can becorrected more properly.

In addition, it is desirable that all the constituent lenses of theimaging lens according to the present invention be made of plasticmaterial. In that case, the imaging lens can be mass-produced, forexample, by injection molding and cost reduction can be achieved.

Furthermore, it is desirable that in the imaging lens according to thepresent invention, no cemented lens be used and an air gap be providedbetween constituent lenses. This configuration makes it possible to formaspheric surfaces on all the constituent lens surfaces so that variousaberrations can be corrected more properly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing the general configuration of animaging lens in Example 1;

FIG. 2 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 1;

FIG. 3 is a schematic view showing the general configuration of animaging lens in Example 2;

FIG. 4 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 2;

FIG. 5 is a schematic view showing the general configuration of animaging lens in Example 3;

FIG. 6 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 3;

FIG. 7 is a schematic view showing the general configuration of animaging lens in Example 4;

FIG. 8 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 4;

FIG. 9 is a schematic view showing the general configuration of animaging lens in Example 5;

FIG. 10 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 5;

FIG. 11 is a schematic view showing the general configuration of animaging lens in Example 6;

FIG. 12 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 6;

FIG. 13 is a schematic view showing the general configuration of animaging lens in Example 7;

FIG. 14 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 7;

FIG. 15 is a schematic view showing the general configuration of animaging lens in Example 8; and

FIG. 16 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a preferred embodiment of the present invention will bedescribed in detail referring to the accompanying drawings.

FIGS. 1, 3, 5, 7, 9, 11, 13, and 15 are schematic views showing thegeneral configurations of the imaging lenses according to Examples 1 to8 of this embodiment respectively. Since all these examples have thesame basic configuration, the configuration of an imaging lens accordingto this embodiment is explained below mainly referring to the schematicview of Example 1.

As shown in FIG. 1, in the imaging lens according to the presentinvention, elements are arranged in the following order from an objectside to an image side: a first lens L1 with positive refractive powerhaving a convex surface on the object side near an optical axis X, asecond lens L2 with negative refractive power having a concave surfaceon the image side near the optical axis X, a third lens L3 with positiverefractive power having a convex surface on the image side near theoptical axis X, a fourth lens L4 with negative refractive power having aconcave surface on the image side near the optical axis X, a fifth lensL5 with positive refractive power as a meniscus lens having a convexsurface on the image side near the optical axis X, a sixth lens L6 as ameniscus double-sided aspheric lens having a concave surface on theimage side near the optical axis X, and a seventh lens L7 with negativerefractive power as a double-sided aspheric lens having a concavesurface on the image side near the optical axis X. An aperture stop STis located on the object side of the first lens L1. Alternatively, theaperture stop ST may be located between the first lens L1 and the secondlens L2 as shown in Example 6.

A filter IR is located between the seventh lens L7 and an image planeIMG. This filter IR is omissible. In the present invention, the totaltrack length is evaluated without the filter IR.

The above imaging lens includes four lens groups, namely a first groupG1 composed of the first lens L1 and the second lens L2 having positivecomposite refractive power, a second group G2 composed of the third lensL3 and the fourth lens L4 having positive composite refractive power, athird group G3 composed of the fifth lens L5 having positive refractivepower, and a fourth group G4 composed of the sixth lens L6 and theseventh lens L7 having negative composite refractive power so that therefractive power arrangement contributes to a shorter total tracklength. Alternatively, the second group G2 may have weak negativecomposite refractive power as shown in Example 4. In each of the firstgroup G1 and the second group G2, the positive lens is located nearer tothe object and the negative lens is located nearer to the image plane sothat chromatic aberrations generated on the positive lens located nearerto the object are properly corrected by the negative lens located nearerto the image plane. The fifth lens L5 which constitutes the third groupG3 has adequate positive refractive power to keep the total track lengthshort and the negative sixth lens L6 and the negative seventh lens L7which constitute the fourth group G4 have adequate aspheric surfaces tofurther correct chromatic aberrations and properly correct fieldcurvature and distortion and control the angle of a chief ray incidenton the image sensor.

The first lens L1 is a biconvex lens in which the curvature radius ofthe object-side surface is smaller than the curvature radius of theimage-side surface and positive refractive power is adequatelydistributed to both the surfaces so as to suppress spherical aberrationsand provide relatively strong refractive power to achieve compactness ofthe imaging lens. Alternatively, the image-side surface of the firstlens L1 may be concave as shown in Example 4 and in that case, it isdesirable that the curvature radius of the image-side surface be largerthan the curvature radius of the object-side surface to the extent thatthe refractive power is not too low and spherical aberrations do notincrease.

The second lens L2 is a lens with negative refractive power which has aconcave surface on the image side near the optical axis X and correctsspherical aberrations and chromatic aberrations properly.

The third lens L3 is a lens with positive refractive power having aconvex surface on the image side near the optical axis X, which correctsfield curvature and coma aberrations properly.

The fourth lens L4 is a lens with negative refractive power having aconcave surface on the image side near the optical axis X, whichcorrects residual chromatic aberrations properly.

The fifth lens L5 is a meniscus lens with positive refractive powerhaving a convex surface on the image side near the optical axis X, whichhas relatively strong positive refractive power. Its refractive power isadequately balanced with the positive refractive power of the first lensL1 so that the imaging lens is compact.

The sixth lens L6 is a meniscus lens having a concave surface on theimage side near the optical axis X, which also corrects residualchromatic aberrations properly. The aspheric surfaces on both the sidesof the lens correct coma aberrations and astigmatism properly.

The seventh lens L7 is a meniscus lens with negative refractive powerhaving a concave surface on the image side near the optical axis x,which ensures an adequate back focus easily. Due to the asphericsurfaces on both the sides of the lens, the negative refractive power ofthe seventh lens L7 decreases toward the peripheral portion of the lensand changes to positive refractive power in the peripheral portion. Thisis effective mainly in correcting distortion and field curvature andcontrolling the angle of a chief ray incident on the image sensor.

The imaging lens according to the present invention satisfiesconditional expressions (1) to (15) below:

50<νd1<70  (1)

20<νd2<30  (2)

50<νd3<70  (3)

20<νd4<30  (4)

0.6<TTL/2ih<1.0  (5)

0.85<Σd/f<1.25  (6)

0.8<ih/f<1.2  (7)

0.7<f1/f<1.5  (8)

−5.0<f2/f<−1.0  (9)

2.0<|f34/f|  (10)

0.6<f5/f<1.2  (11)

−1.2<f67/f<−0.6  (12)

50<νd5<70  (13)

20<νd6<30  (14)

50<νd7<70  (15)

where

-   -   νd1: Abbe number of the first lens L1 at d-ray,    -   νd2: Abbe number of the second lens L2 at d-ray,    -   νd3: Abbe number of the third lens L3 at d-ray,    -   νd4: Abbe number of the fourth lens L4 at d-ray,    -   TTL: distance on the optical axis X from the objet-side surface        of an optical element located nearest to the object to the image        plane IMG without the filter IR, etc.,    -   ih: maximum image height,    -   f: focal length of the overall optical system of the imaging        lens,    -   Σd: distance on the optical axis X from the object-side surface        of the first lens L1 to the image-side surface of the seventh        lens L7,    -   f1: focal length of the first lens L1,    -   f2: focal length of the second lens L2,    -   f34: composite focal length of the third lens L3 and the fourth        lens L4,    -   f5: focal length of the fifth lens L5,    -   f67: composite focal length of the sixth lens L6 and the seventh        lens L7,    -   νd5: Abbe number of the fifth lens L5 at d-ray,    -   νd6: Abbe number of the sixth lens L6 at d-ray, and    -   νd7: Abbe number of the seventh lens L7 at d-ray.

In this embodiment, all the lens surfaces are aspheric. The asphericshapes of these lens surfaces are expressed by the following equation,where Z denotes an axis in the optical axis direction, H denotes aheight perpendicular to the optical axis, k denotes a conic constant,and A4, A6, A8, A10, A12, A14, and A16 denote aspheric surfacecoefficients.

$\begin{matrix}{Z = {\frac{\frac{H^{2}}{R}}{1 + \sqrt{1 - {\left( {k + 1} \right)\frac{H^{2}}{R^{2}}}}} + {A_{4}H^{4}} + {A_{6}H^{6}} + {A_{8}H^{8}} + {A_{10}H^{10}} + {A_{12}H^{12}} + {A_{14}H^{14}} + {A_{16}H^{16}}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

Next, the imaging lenses in examples according to this embodiment willbe explained. In each example, f denotes the focal length of the overalloptical system of the imaging lens, Fno denotes an F-number, ω denotes ahalf field of view, ih denotes a maximum image height, and TTL denotes atotal track length. i denotes a surface number counted from the objectside, r denotes a curvature radius, d denotes the distance between lenssurfaces on the optical axis X (surface distance), Nd denotes arefractive index with respect to d-ray (reference wavelength), and νddenotes an Abbe number with respect to d-ray. As for aspheric surfaces,an asterisk (*) after surface number i indicates that the surfaceconcerned is an aspheric surface.

Example 1

The basic lens data of Example 1 is shown below in Table 1.

TABLE 1 Example 1 in mm f = 6.76 Fno = 2.40 ω(°) = 41.2 ih = 5.99 TTL =9.97 Surface Data Curvature Surface Surface No i Radius r Distance dRefractive Abbe (Object Surface) Infinity Infinity Index Nd Number vd  1(Stop) Infinity −0.15  2* 5.902 0.760 1.5438 55.57  3* −13.378 0.040  4*4.196 0.576 1.6142 25.58  5* 2.657 0.692  6* 28.468 1.381 1.5438 55.57 7* −5.000 0.093  8* −7.763 0.700 1.6142 25.58  9* 36.656 0.389 10*−4.775 1.270 1.5346 56.16 11* −1.976 0.053 12* 14.503 0.790 1.6142 25.5813* 7.785 0.402 14* 6.1147 1.000 1.5346 56.16 15* 2.1731 0.800 16Infinity 0.300 1.5640 51.30 17 Infinity 0.834 Image Plane InfinityConstituent Lens Data Lens Start Surface Focal Length 1 2 7.64 2 4−13.74 3 6 7.94 4 8 −10.37 5 10 5.45 6 12 −28.64 7 14 −6.92 LensComposite Focal Length Third Lens-Fourth Lens 30.08 Sixth Lens-SeventhLens −5.43 Aspheric Surface Data 2nd Surface 3rd Surface 4th Surface 5thSurface 6th Surface 7th Surface 8th Surface k   0.000E+00   0.000E+00  0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00 A4  4.733E−04   7.844E−03 −1.319E−02 −2.924E−02 −2.453E−03 −1.052E−03−1.594E−02 A6 −1.803E−04   5.631E−04   5.781E−03   7.339E−03 −1.303E−03−1.235E−03   1.226E−03 A8 −1.476E−04 −1.398E−03 −2.083E−03 −1.724E−03  3.330E−04   7.037E−05   1.055E−04 A10   2.594E−05   2.751E−04  2.493E−04   1.331E−04   0.000E+00   0.000E+00 −1.756E−05 A12  0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00  0.000E+00 A14   0.000E+00   0.000E+00   0.000E+00   0.000E+00  0.000E+00   0.000E+00   0.000E+00 A16   0.000E+00   0.000E+00  0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00 9th Surface10th Surface 11th Surface 12th Surface 13th Surface 14th Surface 15thSurface k   0.000E+00   0.000E+00 −2.678E+00   0.000E+00   0.000E+00  0.000E+00 −4.569E+00 A4 −1.427E−02   3.293E−03 −8.922E−03   7.763E−04−2.354E−03 −1.419E−02 −7.740E−03 A6   1.694E−03   1.077E−03   1.393E−03−4.500E−04 −1.456E−04   5.646E−04   4.746E−04 A8 −1.569E−04 −1.025E−04  9.563E−05   2.340E−05   3.430E−06   6.271E−06 −2.000E−05 A10  8.620E−06   2.582E−06 −1.118E−05 −2.545E−06 −1.713E−07 −9.263E−07  4.987E−07 A12   0.000E+00   0.000E+00 −6.577E−07   1.037E−07  2.734E−08   1.374E−08 −8.500E−09 A14   0.000E+00   0.000E+00  6.246E−08   0.000E+00 −7.675E−10   2.642E−10   9.622E−11 A16  0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00 −6.317E−12  0.000E+00

As shown in Table 9, the imaging lens in Example 1 satisfies all theconditional expressions (1) to (15).

FIG. 2 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 1. The spherical aberration diagramshows the amount of aberration at wavelengths of F-ray (486 nm), d-ray(588 nm), and C-ray (656 nm). The astigmatism diagram shows the amountof aberration on sagittal image surface S and the amount of aberrationon tangential image surface T (the same is true for FIGS. 4, 6, 8, 10,12, 14, and 16). As shown in FIG. 2, each aberration is properlycorrected.

The imaging lens provides a wide field of view of 80 degrees or more andhigh brightness with an F-value of 2.4. The ratio of total track lengthTTL to maximum image height ih (TTL/2ih) is 0.83, so it achievescompactness though it uses seven constituent lenses.

Example 2

The basic lens data of Example 2 is shown below in Table 2.

TABLE 2 Example 2 in mm f = 6.76 Fno = 2.40 ω(°) = 41.2 ih = 5.99 TTL =9.57 Surface Data Curvature Surface Surface No i Radius r Distance dRefractive Abbe (Object Surface) Infinity Infinity Index Nd Number vd  1(Stop) Infinity −0.185  2* 4.594 0.823 1.5438 55.57  3* −16.373 0.040 4* 5.408 0.500 1.6142 25.58  5* 3.185 0.681  6* −96.794 1.070 1.534656.16  7* −5.000 0.050  8* −13.759 0.700 1.6142 25.58  9* 25.844 0.40210* −3.482 1.170 1.5346 56.16 11* −1.955 0.053 12* 9.153 0.790 1.614225.58 13* 5.035 0.558 14* 5.922 1.055 1.5346 56.16 15* 2.448 0.700 16Infinity 0.300 1.5640 51.30 17 Infinity 0.786 Image Plane InfinityConstituent Lens Data Lens Start Surface Focal Length 1 2 6.69 2 4−13.80 3 6 9.82 4 8 −14.52 5 10 6.58 6 12 −19.65 7 14 −8.73 LensComposite Focal Length Third Lens-Fourth Lens 29.34 Sixth Lens-SeventhLens −5.79 Aspheric Surface Data 2nd Surface 3rd Surface 4th Surface 5thSurface 6th Surface 7th Surface 8th Surface k   0.000E+00   0.000E+00  0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00 A4−5.727E−04   5.079E−03 −1.136E−02 −2.352E−02 −5.571E−03 −1.838E−03−1.684E−02 A6 −9.186E−04 −9.582E−04   4.624E−03   5.871E−03 −1.228E−03−2.322E−03   1.436E−04 A8   1.113E−04 −1.166E−03 −2.286E−03 −1.751E−03−1.266E−04 −1.902E−05 −3.751E−04 A10 −1.114E−04   1.777E−04   3.469E−04  1.681E−04   0.000E+00   0.000E+00   5.333E−05 A12   0.000E+00  0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00A14   0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00  0.000E+00   0.000E+00 A16   0.000E+00   0.000E+00   0.000E+00  0.000E+00   0.000E+00   0.000E+00   0.000E+00 9th Surface 10th Surface11th Surface 12th Surface 13th Surface 14th Surface 15th Surface k  0.000E+00   0.000E+00 −2.608E+00   0.000E+00   0.000E+00   0.000E+00−5.026E+00 A4 −1.445E−02   2.918E−03 −1.281E−02 −5.078E−04 −5.777E−03−1.507E−02 −8.309E−03 A6   9.193E−04   2.119E−03   2.149E−03 −5.507E−04−1.324E−04   5.716E−04   4.648E−04 A8 −1.649E−04 −2.564E−05   1.211E−04  1.930E−05   4.101E−06   7.109E−06 −1.959E−05 A10   2.366E−05−7.078E−06 −1.420E−05 −2.678E−06 −1.940E−07 −9.253E−07   5.065E−07 A12  0.000E+00   0.000E+00 −9.250E−07   1.477E−07   2.571 E−08   1.295E−08−7.576E−09 A14   0.000E+00   0.000E+00   6.974E−08   0.000E+00−7.787E−10   2.428E−10   6.471E−11 A16   0.000E+00   0.000E+00  0.000E+00   0.000E+00   0.000E+00 −5.500E−12   0.000E+00

As shown in Table 9, the imaging lens in Example 2 satisfies all theconditional expressions (1) to (15).

FIG. 4 shows various aberrations of the imaging lens in Example 2. Asshown in FIG. 4, each aberration is corrected properly.

The imaging lens provides a wide field of view of 80 degrees or more andhigh brightness with an F-value of 2.4. The ratio of total track lengthTTL to maximum image height ih (TTL/2ih) is 0.80, so it achievescompactness though it uses seven constituent lenses.

Example 3

The basic lens data of Example 3 is shown below in Table 3.

TABLE 3 Example 3 in mm f = 6.78 Fno = 2.41 ω(°) = 41.1 ih = 5.99 TTL =9.29 Surface Data Curvature Surface Surface No i Radius r Distance dRefractive Abbe (Object Surface) Infinity Infinity Index Nd Number vd  1(Stop) Infinity −0.13  2* 5.019 0.774 1.5438 55.57  3* −6.745 0.068  4*8.549 0.532 1.6349 23.97  5* 3.069 0.700  6* 286.557 0.886 1.5346 56.16 7* −8.053 0.053  8* 7.117 0.600 1.6349 23.97  9* 5.614 0.651 10* −3.9691.097 1.5346 56.16 11* −1.906 0.053 12* 11.711 0.670 1.6349 23.97 13*4.996 0.529 14* 6.2287 1.042 1.5346 56.16 15* 2.4479 0.800 16 Infinity0.300 1.5640 51.30 17 Infinity 0.641 Image Plane Infinity ConstituentLens Data Lens Start Surface Focal Length 1 2 5.42 2 4 −7.83 3 6 15.29 48 −49.56 5 10 5.79 6 12 −14.27 7 14 −8.34 Lens Composite Focal LengthThird Lens-Fourth Lens 20.81 Sixth Lens-Seventh Lens −4.95 AsphericSurface Data 2nd Surface 3rd Surface 4th Surface 5th Surface 6th Surface7th Surface 8th Surface k   0.000E+00   0.000E+00   0.000E+00  0.000E+00   0.000E+00   0.000E+00   0.000E+00 A4 −7.763E−03  6.959E−03 −3.606E−03 −2.401E−02   1.186E−03   8.779E−03 −1.347E−02 A6−3.872E−03 −5.264E−03   5.475E−03   9.046E−03 −2.126E−03 −2.563E−03  9.691E−04 A8   4.450E−04   4.640E−04 −1.164E−03 −1.964E−03   4.475E−05−1.037E−04 −1.584E−04 A10 −1.920E−04 −8.594E−05   1.225E−04   1.736E−04  0.000E+00   0.000E+00 −5.195E−06 A12   0.000E+00   0.000E+00  0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00 A14  0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00  0.000E+00 A16   0.000E+00   0.000E+00   0.000E+00   0.000E+00  0.000E+00   0.000E+00   0.000E+00 9th Surface 10th Surface 11thSurface 12th Surface 13th Surface 14th Surface 15th Surface k  0.000E+00   0.000E+00 −2.633E+00   0.000E+00   0.000E+00   0.000E+00−5.411E+00 A4 −1.794E−02   5.886E−04 −1.181E−02   4.673E−04 −5.650E−03−1.406E−02 −8.527E−03 A6   1.660E−03   1.859E−03   1.900E−03 −6.221E−04−1.948E−04   5.627E−04   4.941E−04 A8 −1.751E−04 −3.802E−05   1.326E−04  1.822E−05   9.028E−06   6.413E−06 −2.174E−05 A10   6.551E−06−4.465E−06 −1.209E−05 −2.795E−06 −1.947E−07 −9.378E−07   5.371E−07 A12  0.000E+00   0.000E+00 −8.523E−07   1.742E−07   2.122E−08   1.374E−08−5.955E−09 A14   0.000E+00   0.000E+00   5.879E−08   0.000E+00−8.130E−10   2.642E−10   3.567E−11 A16   0.000E+00   0.000E+00  0.000E+00   0.000E+00   0.000E+00 −5.954E−12   0.000E+00

As shown in Table 9, the imaging lens in Example 3 satisfies all theconditional expressions (1) to (15).

FIG. 6 shows various aberrations of the imaging lens in Example 3. Asshown in FIG. 6, each aberration is corrected properly.

In addition, the imaging lens provides a wide field of view of 80degrees or more and high brightness with an F-value of 2.4. The ratio oftotal track length TTL to maximum image height ih (TTL/2ih) is 0.78, soit achieves compactness though it uses seven constituent lenses.

Example 4

The basic lens data of Example 4 is shown below in Table 4.

TABLE 4 Example 4 in mm f = 6.91 Fno = 2.40 ω(°) = 40.5 ih = 5.99 TTL =9.51 Surface Data Curvature Surface Surface No. i Radius r Distance dRefractive Abbe (Object Surface) Infinity Infinity Index Nd Number vd  1(Stop) Infinity −0.2  2* 3.909 0.727 1.5438 55.57  3* 500.000 0.053  4*4.925 0.450 1.6349 23.97  5* 3.448 0.603  6* −57.008 1.105 1.5438 55.57 7* −5.000 0.317  8* −5.137 0.600 1.6349 23.97  9* 113.766 0.173 10*−5.583 1.255 1.5346 56.16 11* −2.301 0.053 12* 6.823 0.737 1.6349 23.9713* 6.696 1.028 14* 44.7468 1.000 1.5346 56.16 15* 3.2663 0.800 16Infinity 0.300 1.5640 51.30 17 Infinity 0.422 Image Plane InfinityConstituent Lens Data Lens Start Surface Focal Length 1 2 7.24 2 4−20.54 3 6 10.00 4 8 −7.73 5 10 6.46 6 12 451.08 7 14 −6.65 LensComposite Focal Length Third Lens-Fourth Lens −38.39 Sixth Lens-SeventhLens −7.07 Aspheric Surface Data 2nd Surface 3rd Surface 4th Surface 5thSurface 6th Surface 7th Surface 8th Surface k   0.000E+00   0.000E+00  0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00 A4  2.504E−03   4.631E−03 −1.322E−02 −2.172E−02 −8.638E−03 −2.794E−03−1.772E−02 A6 −6.007E−04   1.143E−03   4.807E−03   4.213E−03 −1.861E−03−2.571E−03 −3.861E−04 A8   5.905E−04 −1.217E−03 −2.279E−03 −1.538E−03−2.196E−04 −3.078E−04 −4.941E−04 A10 −1.954E−04   2.229E−05   1.741E−04  1.088E−04   0.000E+00   0.000E+00   3.213E−05 A12   0.000E+00  0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00A14   0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00  0.000E+00   0.000E+00 A16   0.000E+00   0.000E+00   0.000E+00  0.000E+00   0.000E+00   0.000E+00   0.000E+00 9th Surface 10th Surface11th Surface 12th Surface 13th Surface 14th Surface 15th Surface k  0.000E+00   0.000E+00 −2.803E+00   0.000E+00   0.000E+00   0.000E+00−6.299E+00 A4 −1.741E−02 −1.542E−04 −1.114E−02 −1.283E−03 −3.696E−03−1.326E−02 −8.438E−03 A6   1.286E−03   1.571E−03   1.826E−03 −5.200E−04−2.537E−04   5.940E−04   5.314E−04 A8 −1.585E−04 −4.206E−05   1.158E−04  2.243E−05   5.157E−06   7.406E−06 −2.122E−05 A10   2.416E−05−4.702E−06 −1.314E−05 −2.367E−06 −1.905E−07 −9.038E−07   4.927E−07 A12  0.000E+00   0.000E+00 −8.268E−07   1.112E−07   2.684E−08   1.326E−08−7.646E−09 A14   0.000E+00   0.000E+00   6.918E−08   0.000E+00−5.278E−10   1.455E−10   7.431E−11 A16   0.000E+00   0.000E+00  0.000E+00   0.000E+00   0.000E+00 −3.430E−12   0.000E+00

As shown in Table 9, the imaging lens in Example 4 satisfies all theconditional expressions (1) to (15).

FIG. 8 shows various aberrations of the imaging lens in Example 4. Asshown in FIG. 8, each aberration is corrected properly.

In addition, the imaging lens provides a wide field of view of 80degrees or more and high brightness with an F-value of 2.4. The ratio oftotal track length TTL to maximum image height ih (TTL/2ih) is 0.79, soit achieves compactness though it uses seven constituent lenses.

Example 5

The basic lens data of Example 5 is shown below in Table 5.

TABLE 5 Example 5 in mm f = 6.878 Fno = 2.40 ω(°) = 40.7 ih = 5.99 TTL =9.51 Surface Data Curvature Surface Surface No i Radius r Distance dRefractive Abbe (Object Surface) Infinity Infinity Index Nd Number vd  1(Stop) Infinity −0.15  2* 4.675 0.859 1.5438 55.57  3* −8.414 0.062  4*−200.000 0.450 1.6349 23.97  5* 7.659 0.786  6* −21.168 0.691 1.543855.57  7* −7.732 0.050  8* 21.372 0.600 1.6349 23.97  9* 9.658 0.490 10*−3.936 1.255 1.5346 56.16 11* −1.916 0.053 12* 10.446 0.700 1.6349 23.9713* 4.872 0.620 14* 5.8439 1.076 1.5346 56.16 15* 2.3606 0.800 16Infinity 0.300 1.5640 51.30 17 Infinity 0.825 Image Plane InfinityConstituent Lens Data Lens Start Surface Focal Length 1 2 5.66 2 4−11.61 3 6 22.00 4 8 −28.32 5 10 5.74 6 12 −15.12 7 14 −8.30 LensComposite Focal Length Third Lens-Fourth Lens 91.65 Sixth Lens-SeventhLens −5.03 Aspheric Surface Data 2nd Surface 3rd Surface 4th Surface 5thSurface 6th Surface 7th Surface 8th Surface k   0.000E+00   0.000E+00  0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00 A4−2.432E−03   4.564E−03 −8.319E−03 −2.155E−02 −7.998E−03   2.520E−03−1.669E−02 A6 −2.089E−03 −2.681E−04   5.956E−03   5.035E−03 −2.370E−03−2.179E−03   3.460E−04 A8   7.323E−04 −1.270E−03 −2.557E−03 −1.393E−03  6.397E−05 −1.145E−04 −3.424E−04 A10 −3.283E−04 −5.908E−05   1.074E−04  1.608E−05   0.000E+00   0.000E+00   1.356E−05 A12   0.000E+00  0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00A14   0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00  0.000E+00   0.000E+00 A16   0.000E+00   0.000E+00   0.000E+00  0.000E+00   0.000E+00   0.000E+00   0.000E+00 9th Surface 10th Surface11th Surface 12th Surface 13th Surface 14th Surface 15th Surface k  0.000E+00   0.000E+00 −2.666E+00   0.000E+00   0.000E+00   0.000E+00−4.955E+00 A4 −1.691E−02   1.727E−03 −1.334E−02 −3.078E−04 −6.574E−03−1.543E−02 −8.384E−03 A6   9.317E−04   1.965E−03   1.895E−03 −5.628E−04−9.109E−05   5.717E−04   4.834E−04 A8 −1.628E−04 −4.420E−05   1.214E−04  1.934E−05   5.202E−06   7.067E−06 −2.101E−05 A10   2.288E−05−8.083E−06 −1.279E−05 −2.787E−06 −2.477E−07 −9.246E−07   4.973E−07 A12  0.000E+00   0.000E+00 −7.944E−07   1.451E−07   2.263E−08   1.347E−08−7.305E−09 A14   0.000E+00   0.000E+00   7.298E−08   0.000E+00−7.679E−10   2.033E−10   8.752E−11 A16   0.000E+00   0.000E+00  0.000E+00   0.000E+00   0.000E+00 −4.363E−12   0.000E+00

As shown in Table 9, the imaging lens in Example 5 satisfies all theconditional expressions (1) to (15).

FIG. 10 shows various aberrations of the imaging lens in Example 5. Asshown in FIG. 10, each aberration is corrected properly.

In addition, the imaging lens provides a wide field of view of 80degrees or more and high brightness with an F-value of 2.4. The ratio oftotal track length TTL to maximum image height ih (TTL/2ih) is 0.79, soit achieves compactness though it uses seven constituent lenses.

Example 6

The basic lens data of Example 6 is shown below in Table 6.

TABLE 6 Example 6 in mm f = 6.784 Fno = 2.41 ω(°) = 41.1 ih = 5.99 TTL =9.79 Surface Data Curvature Surface Surface No i Radius r Distance dRefractive Abbe (Object Surface) Infinity Infinity Index Nd Number vd 1* 6.551 0.656 1.5438 55.57  2* −19.094 −0.009  3 (Stop) Infinity 0.050 4* 3.420 0.465 1.6142 25.58  5* 2.777 0.592  6* −61.014 1.211 1.534656.16  7* −3.500 0.052  8* −7.043 0.867 1.6142 25.58  9* 20.788 0.50310* −3.693 1.224 1.5346 56.16 11* −1.929 0.053 12* 16.832 0.829 1.614225.58 13* 7.928 0.537 14* 6.4006 1.000 1.5346 56.16 15* 2.3387 0.800 16Infinity 0.300 1.5640 51.30 17 Infinity 0.773 Image Plane InfinityConstituent Lens Data Lens Start Surface Focal Length 1 1 9.05 2 4−33.18 3 6 6.89 4 8 −8.46 5 10 6.08 6 12 −25.30 7 14 −7.54 LensComposite Focal Length Third Lens-Fourth Lens 34.16 Sixth Lens-SeventhLens −5.61 Aspheric Surface Data 1st Surface 2nd Surface 4th Surface 5thSurface 6th Surface 7th Surface 8th Surface k   0.000E+00   0.000E+00  0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00 A4  2.835E−03   4.028E−03 −1.959E−02 −2.873E−02 −1.476E−03 −4.280E−04−2.070E−02 A6 −1.993E−03 −3.504E−04   4.377E−03   4.153E−03 −1.217E−03−2.006E−03   5.450E−05 A8   7.500E−04 −4.328E−04 −1.640E−03 −1.392E−03−1.763E−04 −2.511E−04 −4.224E−04 A10 −1.947E−04 −2.621E−05   7.274E−05  4.673E−05   0.000E+00   0.000E+00   5.841E−05 A12   0.000E+00  0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00A14   0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00  0.000E+00   0.000E+00 A16   0.000E+00   0.000E+00   0.000E+00  0.000E+00   0.000E+00   0.000E+00   0.000E+00 9th Surface 10th Surface11th Surface 12th Surface 13th Surface 14th Surface 15th Surface k  0.000E+00   0.000E+00 −2.602E+00   0.000E+00   0.000E+00   0.000E+00−4.830E+00 A4 −1.648E−02   1.209E−03 −1.182E−02   2.749E−03 −3.373E−03−1.657E−02 −8.723E−03 A6   1.379E−03   1.954E−03   1.760E−03 −7.283E−04−1.473E−04   6.112E−04   5.285E−04 A8 −1.328E−04 −3.294E−05   1.226E−04  3.110E−05   5.120E−06   8.132E−06 −2.169E−05 A10   1.979E−05−4.819E−06 −1.221E−05 −1.901E−06 −2.920E−07 −9.332E−07   5.060E−07 A12  0.000E+00   0.000E+00 −8.281E−07   6.359E−08   2.409E−08   1.231 E−08−6.843E−09 A14   0.000E+00   0.000E+00   5.965E−08   0.000E+00−5.741E−10   2.203E−10   5.440E−11 A16   0.000E+00   0.000E+00  0.000E+00   0.000E+00   0.000E+00 −4.533E−12   0.000E+00

As shown in Table 9, the imaging lens in Example 6 satisfies all theconditional expressions (1) to (15).

FIG. 12 shows various aberrations of the imaging lens in Example 6. Asshown in FIG. 12, each aberration is corrected properly.

The imaging lens provides a wide field of view of 80 degrees or more andhigh brightness with an F-value of 2.4. The ratio of total track lengthTTL to maximum image height ih (TTL/2ih) is 0.82, so it achievescompactness though it uses seven constituent lenses.

Example 7

The basic lens data of Example 7 is shown below in Table 7.

TABLE 7 Example 7 in mm f = 3.452 Fno = 2.01 ω(°) = 40.0 ih = 2.93 TTL =4.82 Surface Data Curvature Surface Surface No i Radius r Distance dRefractive Abbe (Object Surface) Infinity Infinity Index Nd Number vd  1(Stop) Infinity −0.12  2* 2.409 0.531 1.5438 55.57  3* −7.584 0.020  4*3.487 0.290 1.6349 23.97  5* 1.921 0.360  6* −21.075 0.509 1.5346 56.16 7* −3.212 0.025  8* −9.795 0.300 1.6349 23.97  9* 47.382 0.204 10*−1.594 0.554 1.5346 56.16 11* −0.855 0.026 12* 3.668 0.317 1.6349 23.9713* 2.395 0.131 14* 2.8544 0.430 1.5346 56.16 15* 1.0356 0.400 16Infinity 0.210 1.5640 51.30 17 Infinity 0.589 Image Plane InfinityConstituent Lens Data Lens Start Surface Focal Length 1 2 3.43 2 4 −7.263 6 7.02 4 8 −12.76 5 10 2.74 6 12 −12.03 7 14 −3.31 Lens CompositeFocal Length Third Lens-Fourth Lens 15.60 Sixth Lens-Seventh Lens −2.56Aspheric Surface Data 2nd Surface 3rd Surface 4th Surface 5th Surface6th Surface 7th Surface 8th Surface k   0.000E+00   0.000E+00  0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00 A4−6.534E−04 −1.764E−03 −1.274E−01 −1.846E−01 −5.965E−02 −8.331E−02−1.701E−01 A6 −2.111E−02   6.379E−02   1.520E−01   1.112E−01 −8.220E−02−4.934E−02   2.576E−02 A8   3.737E−02 −1.818E−01 −2.428E−01 −1.432E−01  1.301E−02   1.734E−02 −7.037E−03 A10 −5.338E−02   5.655E−02  6.957E−02   2.448E−02   0.000E+00   0.000E+00   2.402E−03 A12  0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00  0.000E+00 A14   0.000E+00   0.000E+00   0.000E+00   0.000E+00  0.000E+00   0.000E+00   0.000E+00 A16   0.000E+00   0.000E+00  0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00 9th Surface10th Surface 11th Surface 12th Surface 13th Surface 14th Surface 15thSurface k   0.000E+00   0.000E+00 −2.790E+00   0.000E+00   0.000E+00  0.000E+00 −5.955E+00 A4 −1.195E−01   8.022E−02 −9.767E−02 −4.089E−02−7.313E−02 −1.260E−01 −7.527E−02 A6   4.895E−02   5.987E−02   8.116E−02−1.783E−02 −6.540E−03   2.021E−02   2.177E−02 A8 −3.118E−02 −4.834E−03  1.606E−02   4.733E−03   1.498E−03   1.023E−03 −3.616E−03 A10  1.489E−02 −3.066E−03 −9.396E−03 −1.866E−03 −2.527E−05 −5.930E−04  2.765E−04 A12   0.000E+00   0.000E+00 −2.518E−03   3.970E−04  6.254E−05   3.388E−05 −1.611E−05 A14   0.000E+00   0.000E+00  8.407E−04   0.000E+00 −1.195E−05   3.746E−06   1.267E−06 A16  0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00 −3.570E−07  0.000E+00

As shown in Table 9, the imaging lens in Example 7 satisfies all theconditional expressions (1) to (15).

FIG. 14 shows various aberrations of the imaging lens in Example 7. Asshown in FIG. 14, each aberration is corrected properly.

In addition, the imaging lens provides a wide field of view of 80degrees or more and high brightness with an F-value of 2.0. The ratio oftotal track length TTL to maximum image height ih (TTL/2ih) is 0.82, soit achieves compactness though it uses seven constituent lenses.

Example 8

The basic lens data of Example 8 is shown below in Table 8.

TABLE 8 Example 8 in mm f = 6.781 Fno = 2.41 ω(°) = 41.1 ih = 5.99 TTL =9.53 Surface Data Curvature Surface Surface No i Radius r Distance dRefractive Abbe (Object Surface) Infinity Infinity Index Nd Number vd  1(Stop) Infinity −0.13  2* 5.591 0.683 1.5438 55.57  3* −9.809 0.040  4*5.913 0.545 1.6349 23.97  5* 3.081 0.721  6* −50.310 1.051 1.5438 55.57 7* −5.000 0.050  8* 10.044 0.600 1.6349 23.97  9* 6.265 0.646 10*−3.634 1.187 1.5438 55.57 11* −1.933 0.053 12* 12.725 0.700 1.6349 23.9713* 5.078 0.559 14* 6.6328 1.048 1.5438 55.57 15* 2.5287 0.800 16Infinity 0.300 1.5640 51.30 17 Infinity 0.651 Image Plane InfinityConstituent Lens Data Lens Start Surface Focal Length 1 2 6.65 2 4−10.95 3 6 10.13 4 8 −27.95 5 10 6.09 6 12 −13.80 7 14 −8.26 LensComposite Focal Length Third Lens-Fourth Lens 15.02 Sixth Lens-SeventhLens −4.84 Aspheric Surface Data 2nd Surface 3rd Surface 4th Surface 5thSurface 6th Surface 7th Surface 8th Surface k   0.000E+00   0.000E+00  0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00 A4−4.481E−03   5.909E−03 −7.624E−03 −2.388E−02 −1.587E−03   3.146E−03−1.446E−02 A6 −2.518E−03 −2.178E−03   5.403E−03   7.201E−03 −2.098E−03−2.274E−03   7.969E−04 A8   6.727E−04 −5.293E−04 −1.979E−03 −1.836E−03  4.720E−05 −1.889E−05 −1.764E−04 A10 −2.386E−04   3.757E−05   2.468E−04  1.481E−04   0.000E+00   0.000E+00   1.096E−05 A12   0.000E+00  0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00A14   0.000E+00   0.000E+00   0.000E+00   0.000E+00   0.000E+00  0.000E+00   0.000E+00 A16   0.000E+00   0.000E+00   0.000E+00  0.000E+00   0.000E+00   0.000E+00   0.000E+00 9th Surface 10th Surface11th Surface 12th Surface 13th Surface 14th Surface 15th Surface k  0.000E+00   0.000E+00 −2.635E+00   0.000E+00   0.000E+00   0.000E+00−5.592E+00 A4 −1.687E−02   1.502E−03 −1.141E−02 −2.939E−04 −6.354E−03−1.420E−02 −8.556E−03 A6   1.362E−03   2.005E−03   1.870E−03 −5.167E−04−1.230E−04   5.713E−04   5.076E−04 A8 −1.744E−04 −3.060E−05   1.255E−04  1.423E−05   7.868E−06   6.648E−06 −2.127E−05 A10   1.325E−05−4.709E−06 −1.251E−05 −2.682E−06 −2.382E−07 −9.358E−07   5.086E−07 A12  0.000E+00   0.000E+00 −8.425E−07   1.745E−07   2.180E−08   1.327E−08−6.517E−09 A14   0.000E+00   0.000E+00   6.556E−08   0.000E+00−7.869E−10   2.601E−10   5.919E−11 A16   0.000E+00   0.000E+00  0.000E+00   0.000E+00   0.000E+00 −5.510E−12   0.000E+00

As shown in Table 9, the imaging lens in Example 8 satisfies all theconditional expressions (1) to (15).

FIG. 16 shows various aberrations of the imaging lens in Example 8. Asshown in FIG. 16, each aberration is corrected properly.

In addition, the imaging lens provides a wide field of view of 80degrees or more and high brightness with an F-value of 2.4. The ratio oftotal track length TTL to maximum image height ih (TTL/2ih) is 0.79, soit achieves compactness though it uses seven constituent lenses.

As explained above, the imaging lenses according to this embodiment ofthe present invention realize an imaging lens system which provides awide field of view of 80 degrees or more and high brightness with anF-value of 2.0 to 2.4 and corrects aberrations properly. In addition,the ratio of total track length TTL to maximum image height ih (TTL/2ih)is 0.85 or less, offering a compact lens system.

Table 9 shows data on Examples 1 to 8 in relation to the conditionalexpressions (1) to (15).

TABLE 9 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6Example 7 Example 8 Conditional Expression (1) 55.57 55.57 55.57 55.5755.57 55.57 55.57 55.57 50 < vd1 < 70 Conditional Expression (2) 25.5825.58 23.97 23.97 23.97 25.58 23.97 23.97 20 < vd2 < 30 ConditionalExpression (3) 55.57 56.16 56.16 55.57 55.57 56.16 56.16 55.57 50 < vd3< 70 Conditional Expression (4) 25.58 25.58 23.97 23.97 23.97 25.5823.97 23.97 20 < vd4 < 30 Conditional Expression (5) 0.83 0.80 0.78 0.790.79 0.82 0.82 0.79 0.6 < TTL/2ih < 1.0 Conditional Expression (6) 1.201.17 1.13 1.17 1.12 1.18 1.07 1.16 0.85 < Σd/f < 1.25 ConditionalExpression (7) 0.89 0.89 0.88 0.87 0.87 0.88 0.85 0.88 0.8 < ih/f < 1.2Conditional Expression (8) 1.13 0.99 0.80 1.05 0.82 1.33 0.99 0.98 0.7 <f1/f < 1.5 Conditional Expression (9) −2.03 −2.04 −1.16 −2.97 −1.69−4.89 −2.10 −1.61 −5.0 < f2/f < −1.0 Conditional Expression (10) 4.454.34 3.07 5.55 13.33 5.04 4.52 2.22 2.0 < | f34/f | ConditionalExpression (11) 0.81 0.97 0.85 0.93 0.83 0.90 0.79 0.90 0.6 < f5/f < 1.2Conditional Expression (12) −0.80 −0.86 −0.73 −1.02 −0.73 −0.83 −0.74−0.71 −1.2 < f67/f < −0.6 Conditional Expression (13) 56.16 56.16 56.1656.16 56.16 56.16 56.16 55.57 50 < vd5 < 70 Conditional Expression (14)25.58 25.58 23.97 23.97 23.97 25.58 23.97 23.97 20 < vd6 < 30Conditional Expression (15) 56.16 56.16 56.16 56.16 56.16 56.16 56.1655.57 50 < vd7 < 70

The imaging lens composed of seven constituent lenses according to thepresent invention features compactness and a wide field of view andmeets the demand for high resolution. Particularly when it is used in ahighly functional product such as a smart TV or 4K TV, or an informationterminal such as a game console or PC, or an increasingly compact andlow-profile mobile terminal such as a smart phone, mobile phone or PDA(Personal Digital Assistant), it enhances the performance of the productin which it is mounted.

The effects of the present invention are as follows.

According to the present invention, it is possible to provide ahigh-brightness compact imaging lens which delivers higher opticalperformance than conventional imaging lenses when it is used not only ina conventional small image sensor but also in a large image sensor, andprovides a wide field of view and can correct various aberrationsproperly.

What is claimed is:
 1. An imaging lens in which elements are arranged inorder from an object side to an image side, comprising: a first lenswith positive refractive power; a second lens with negative refractivepower; a third lens; a fourth lens; a fifth lens; a sixth lens having aconcave surface on the image side near an optical axis; and a seventhlens with negative refractive power.
 2. The imaging lens according toclaim 1, wherein the first lens has a convex surface on the object sidenear the optical axis, and the second lens has a concave surface on theimage side near the optical axis.
 3. The imaging lens according to claim1, wherein the third lens has positive refractive power with a convexsurface facing the image side near the optical axis, and the fourth lenshas negative refractive power with a concave surface facing the imageside near the optical axis.
 4. The imaging lens according to claim 1,wherein the fifth lens is a meniscus lens with positive refractive powerhaving a convex surface on the image side near the optical axis.
 5. Theimaging lens according to claim 1, wherein the sixth lens is a meniscusdouble-sided aspheric lens, having a pole-change point in a position offthe optical axis on the object-side surface and the image-side surfacethereof, and the seventh lens is a double-sided aspheric lens with aconcave surface facing the image side near the optical axis, having apole-change point in a position off the optical axis on the image-sidesurface thereof.
 6. The imaging lens according to claim 1, whereinconditional expressions (1) and (2) below are satisfied;50<νd1<70  (1)20<νd2<30  (2) where νd1; Abbe number of the first lens at d-ray, andνd2: Abbe number of the second lens at d-ray.
 7. The imaging lensaccording to claim 1, wherein conditional expressions (3) and (4) beloware satisfied;50<νd3<70  (3)20<νd4<30  (4) where νd3: Abbe number of the third lens at d-ray, andνd4: Abbe number of the fourth lens at d-ray.
 8. The imaging lensaccording to claim 1, wherein a conditional expression (5) below issatisfied;0.6<TTL/2ih<1.0  (5) where TTL: distance on the optical axis from anobject-side surface of an optical element located nearest to an objectto an image plane without a filter or the like, and ih: maximum imageheight.
 9. The imaging lens according to claim 1, wherein a conditionalexpression (6) below is satisfied;0.85<Σd/f<1.25  (6) where f: focal length of an overall optical systemof the imaging lens, and Σd: distance on the optical axis from theobject-side surface of the first lens to the image-side surface of theseventh lens.
 10. The imaging lens according to claim 1, wherein aconditional expression (7) below is satisfied;0.8<ih/f<1.2  (7) where f: focal length of an overall optical system ofthe imaging lens, and ih: maximum image height.
 11. The imaging lensaccording to claim 1, wherein conditional expressions (8) and (9) beloware satisfied;0.7<f1/f<1.5  (8)−5.0<f2/f<−1.0  (9) where f: focal length of an overall optical systemof the imaging lens, f1: focal length of the first lens, and f2: focallength of the second lens.
 12. The imaging lens according to claim 1,wherein a conditional expression (10) below is satisfied;2.0<|f34/f|  (10) where f: focal length of an overall optical system ofthe imaging lens, and f34: composite focal length of the third lens andthe fourth lens.
 13. The imaging lens according to claim 1, whereinconditional expressions (11) and (12) below are satisfied;0.6<f5/f<1.2  (11)−1.2<f67/f<−0.6  (12) where f: focal length of an overall optical systemof the imaging lens, f5: focal length of the fifth lens, and f67:composite focal length of the sixth lens and the seventh lens.
 14. Theimaging lens according to claim 1, wherein conditional expressions (13),(14), and (15) below are satisfied;50<νd5<70  (13)20<νd6<30  (14)50<νd7<70  (15) where νd5: Abbe number of the fifth lens at d-ray, νd6:Abbe number of the sixth lens at d-ray, and νd7: Abbe number of theseventh lens at d-ray.
 15. An imaging lens in which elements arearranged in order from an object side to an image side, comprising: afirst lens with positive refractive power having a biconvex shape nearan optical axis; a second lens; a third lens; a fourth lens; a fifthlens; a sixth lens as a double-sided aspheric lens having a convexsurface on the object side near the optical axis; and a seventh lenswith negative refractive power as a meniscus double-sided aspheric lens;wherein a conditional expression (10) below is satisfied;2.0<|f34/f|  (10) where f: focal length of an overall optical system ofthe imaging lens, and f34: composite focal length of the third lens andthe fourth lens.
 16. The imaging lens according to claim 15, wherein thesecond lens has negative refractive power with a concave surface facingthe image side near the optical axis.
 17. The imaging lens according toclaim 15, wherein the third lens has positive refractive power with aconvex surface facing the image side near the optical axis, and thefourth lens has negative refractive power with a concave surface facingthe image side near the optical axis.
 18. The imaging lens according toclaim 15, wherein the fifth lens is a meniscus lens with positiverefractive power having a convex surface on the image side near theoptical axis.
 19. The imaging lens according to claim 15, wherein thesixth lens is a meniscus lens, having a pole-change point in a positionoff the optical axis on the object-side surface and the image-sidesurface thereof, and the seventh lens has a concave surface on the imageside near the optical axis, having a pole-change point in a position offthe optical axis on the image-side surface thereof.
 20. The imaging lensaccording to claim 15, wherein a conditional expression (5) below issatisfied;0.6<TTL/2ih<1.0  (5) where TTL: distance on the optical axis from anobject-side surface of an optical element located nearest to an objectto an image plane without a filter or the like, and ih: maximum imageheight.